| Jurisdiction: | Diocese |
| Oita | |
| Local: | Japanese: カトリック大分教区 |
| Latin: | Dioecesis Oitaensis |
| Country: | Japan |
| Territory: | Ōita and Miyazaki |
| Metropolitan: | Nagasaki 長崎 |
| Province: | Nagasaki 長崎 |
| Rite: | Latin Rite |
| Cathedral: | St Francis Xavier Cathedral in Ōita |
| Area Km2: | 14,072 |
| Population: | 2,368,659 |
| Population As Of: | 2004 |
| Catholics: | 5,764 |
| Catholics Percent: | 0.2 |
| Bishop: | Sulpizio Shinzo Moriyama |
| Bishop Title: | Bishop |
| Metro Archbishop: | Peter Michiaki Nakamura |
| Map: | Giappone - Diocesi di Oita.png |
| Website: | Website of the Diocese |
The Diocese of Oita (Latin: Dioecesis Oitaensis, Japanese: カトリック大分教区|Katorikku Ōita Kyōku) is a suffragan Latin Church diocese of the Catholic Church in the ecclesiastical province of the metropolitan Nagasaki in southern Japan.
Its cathedral episcopal see is the Cathedral of St. Francis Xavier (Oita Church), in the city of Ōita.
The first Catholic jurisdiction of Otai's territory was established on 19 February 1588, during Portuguese colonial prominence and missionary efforts in the Far East, as the Diocese of Funai (or Funay), on territory split off from the colonial Roman Catholic Diocese of Macau.
It was suppressed around 1660, having had the following incumbents (all Portuguese missionary members of Latin Congregations):